1. Technical Field
The present invention relates to a self-oscillation circuit having a means for eliminating a quadrature error and a method for eliminating a quadrature error using the circuit, and more particularly, to a self-oscillation circuit having a means for eliminating a quadrature error, which eliminates a quadrature error signal that occurs due to a mismatch caused by an asymmetrical shape of a gyroscope sensor to prevent a signal saturation and eliminate noises, and a method for eliminating a quadrature error using the circuit.
2. Description of the Related Art
A gyroscope is an apparatus which measures an angular velocity using a Coriolis force of a vibrating object. The Coriolis force depends on the following Equation 1.F=2 mVΩ  [Equation 1]
In the above Equation 1, F represents a Coriolis force, m represents a mass, V represents a velocity, and Ω represents an angular velocity.
The angular velocity Ω represented by F/2 mV may be obtained by measuring the F when a constant velocity V is imposed on an object. In order for an object to obtain the constant velocity V, a vibration type gyroscope uses a feedback system which is self-oscillated. The self-oscillation happens under the condition in which the phase of the feedback loop becomes 180° and an open loop gain is larger than 1. When a driving signal of a resonance frequency is applied to the gyroscope sensor, an output phase of the sensor is shifted by 90° and output. Therefore, in order for the gyroscope sensor to perform the self-oscillation, when the gyroscope sensor uses a phase shifter to delay a phase by 90°, a phase is shifted by 180° in total, such that the gyroscope sensor may be self-oscillated.
As illustrated in FIG. 1, a process of processing a signal output from the gyroscope sensor includes amplifying, by a pre-amplifier 102, a signal output from a gyroscope sensor 101, demodulating, by a demodulator 103, the amplified signal, eliminating, by a low pass filter 104, a high frequency noise from the demodulated signal, and converting, by an analog/digital converter 105, the noise-removed signal (analog signal) into a digital data.
In a series of processes as described above, a quadrature error occurs due to a mismatch caused by an asymmetrical shape of the gyroscope sensor 101. When the gyroscope sensor is normally operated, the quadrature error is eliminated due to the demodulation process.
However, when the quadrature error is large, a signal is saturated as illustrated in FIG. 2. As a result, it may be difficult to detect the signal. Further, the quadrature error gives rise to noises (for example, jitter) in a system to hinder an accurate signal detection.